import hashlib as hasher
import datetime as date


class Block:
    def __init__(self, index, timestamp, data, previous_hash):
        self.index = index
        self.timestamp = timestamp
        self.data = data
        self.previous_hash = previous_hash
        self.hash = self.hash_block()

    def hash_block(self):
        sha = hasher.sha256()
        sha.update(str(self.index) +
                   str(self.timestamp) +
                   str(self.data) +
                   str(self.previous_hash))
        return sha.hexdigest()


def create_genesis_block():
    # Manually construct ablock with
    # index zero andarbitrary previous hash
    return Block(0, date.datetime.now(), "GenesisBlock", "0")


def next_block(last_block):
    this_index = last_block.index + 1

    this_timestamp = date.datetime.now()

    this_data = "Hey! I'm block " + str(this_index)

    this_hash = last_block.hash

    return Block(this_index, this_timestamp, this_data, this_hash)


# Create the blockchain and add the genesis block

blockchain = [create_genesis_block()]

previous_block = blockchain[0]

# How many blocks should we add to the chain

# after the genesis block

num_of_blocks_to_add = 20

# Addblocks to the chain

for i in range(0, num_of_blocks_to_add):
    block_to_add = next_block(previous_block)

    blockchain.append(block_to_add)

    previous_block = block_to_add

    # Telleveryone about it!

    print("Block #{} has been added to theblockchain!".format(block_to_add.index))

    print("Hash:{}\n".format(block_to_add.hash))
